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UNIVERSITY  OF  ILLINOIS  BULLETIN 

Vol.  V.  AUGUST.  17,  1908  No.  39b 

[Entered   February  14,  1902,  at  Urbana,  Illinois,  as  second-class  matter 
under  Act  of  Congress  of  July  16th,  1894. 


BULLETIN  No.  8.     DEPARTMENT  OF  CERAMICS 

C.    W.    ROLFE,   Director 


A  Study  of  the  Heat  Distribution  in  Four 
Industrial  Kilns. 


By  A.  V.  BLEININGER 


I  907-  J  908 


PUBLISHED    FORTNIGHTLY   BY  THE   UNIVERSITY 


A  STUDY  OF  THE  HEAT  DISTRIBUTION  IN  FOUR 
INDUSTRIAL  KILNS. 

BY 

A.  V.  Bleininger^  Champaign,  Illinois. 

There  is  a  decided  lack  of  data  in  regard  to  the  con- 
sumption of  fuel  in  periodic  ceramic  kilns,  expressed  in 
accurate  terms,  as  well  as  with  respect  to  the  way  in  Avhich 
tlie  heat  is  distributed.  It  was  hence  thought  advisable  to 
undertake  the  exanunation  of  several  kilns  for  the  purpose 
of  determining  the  ratio  between  the  heat  made  useful  and 
that  escaping  as  waste.  The  kilns  studied  represented  sev 
eral  types  and  widely  ditteriug  conditions,  one  of  them 
being  a  sewer  pipe,  one  a  paving  brick,  and  two,  terra  cotta 
muffle  kilns,  entirely  unlike  in  construction.  In  addition 
a  building  brick  kiln  was  examined,  which  has  already 
been  reported  upon  elsewhere,* 

In  making  a  heat  balance  of  a  kilns  we  must  determine 
the  following  factors: 

A.  Heat  introduced  as  fuel. 

B.  Heat  lost  by  the  waste  gases. 

C.  Heat  lost  by  the  unburnt  fuel  in  the  ashes. 

D.  Heat  used  in  the  burning  of  the  ware. 

E.  Heat  taken  up  by  the  kiln  and  lost  by  I'adiation. 

The  last  factor,  important  though  it  is,  cannot  be  es- 
timated by  any  direct  means  available,  since  the  difficulties 
opposed  to  its  determination  are  too  great.  We  must  bo 
satisfied  to  obtain  it  by  difference.  For,  since  the  first 
four  items  are  readily  obtainable  by  measurement,  the  fifth 
is  arrived  at  by  the  evident  relation : 

E=A— (B+C+D). 


*"The  Balance  Sheet  of  a  Down  Draft  Kiln,"  Clay  Worker,  February, 
1908.    Read  before  the  N.  B.  M.  A. 


4  A    STUDY    OF    HEAT    DISTRIBUTION     IN     FOUR    INDUSTKIAI.    KILNS. 

A.  The  heat  introduced  as  fuel  was  of  course  readily 
calcuhited  from  tlie  weight  of  the  coal  used  from  day  to 
day.  The  calorific  value  of  the  latter  was  obtained  by 
determining  the  heating  value  of  a  well  averaged  sample 
of  the  fuel  in  the  calorimeter.  This  work  aars  done  in  the 
department  of  industrial  chemistry  at  the  University  of 
Illinois,  under  the  direction  of  Professor  Parr.  The  weight 
of  the  coal  multiplied  by  its  heating  value  gave  the  total 
number  of  calories  introduced. 

B.  The  heat  carried  out  by  the  waste  gases  was  cal 
culated  from  the  daily  coal  consumption,  the  ultimate 
analysis  of  the  coal,  the  analysis  of  the  stack  gases,  the 
thermal  capacity  of  the  gases  and  the  flue  temperature. 
The  first  factor  was,  of  course,  easily  determined  by  weigh- 
ing the  coal,  the  second  by  the  ultimate  analysis  of  the 
coal,  this  work  having  been  carried  out  in  the  de])artinent 
of  chemistry  under  Professor  Parr,  the  third  by  the  analy- 
sis of  the  flue  gases,  using  the  Orsat  apparatus,  the  fourth 
from  known  data,  and  the  fifth  by  means  of  the  Le  Cliate- 
lier  thermocouple  applied  in  the  flue  as  close  to  the  kiln 
as  possible. 

The  daily  coal  consumption  permitted  of  calculating 
the  weight  of  coal  fired  per  hour  for  a  certain  period,  which 
was,  for  the  sake  of  convenience,  taken  as  twelve  hours. 
This  period  was  considered  the  unit  in  all  the  calculations. 

From  the  ultimate  analysis,  allowing  for  the  carbon 
escaping  Avith  the  ashes,  the  weight  of  the  gases  evolved 
with  theoretical  air  supply  was  calculated.  If,  for  instance, 
the  coal  had  the  following  composition  : 

Carbon     60.15% — 3-03    (lost   in   ashes)=57. 12% 

Hydrogen     415% 

Oxygen     9-37% 

Sulphur     4-34% — 1-30    (lost   in   ashes)  =  3.04% 

IMoisture     7.90% 

Ash     14.09% 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  O 

1  kg.  of  coal  Avould  result,  on  burning  with  just  tlie  requi- 
site amount  of  air,  in 

0.5712.^1  =  2  09  kg:   of  carbon  dioxide 
0  0415.9  f  0.079  =  0.453  kg.  of  steam 

0.0304  X    2  =  0  060  kg.  of  sulphur  oxide 
0.5712.»|X   3   35  =  5  900  kg.  of  nitrogen 

The  weight  of  air  required  for  the  combustion  of  1  kg. 
cf  this  coal  would  then  l)e  7.66  kg. 

The  tiue  gas  analysis  was  simply  made  for  the  purpose 
of  determining  the  amount  of  excess  air  introduced  into 
tlie  kiln,  as  this  evidently  changes  the  weight  of  the  gases 
resulting  from  1  kg.  of  the  coal  materially.  It  was  en- 
deavored to  take  sam])lcs  from  the  flue  so  that  they  repre- 
sented average  conditions,  and  from  twd  to  three  analyses 
were  made  each  hour.  This  meant  the  making  of  hundreds 
of  analyses  during  each  burn.  As  the  basis  of  the  calcula- 
tion of  the  excess  air  present  tlie  oxygen  found  was  used 
according  to  the  relation  : 

Coefficient  of  air-admission= 


100— 4.76X 9f;  Oxygen. 

To  illustrate:  Supposing  the  gas  was  found  to  con- 
tain 5%  of  oxygen.    AVe  would  have  then  : 

]Oo  —  4  76 N- 5  =^-'^^,  rcpi-esenting  total  aii-  admitted. 

The  excess  air  jnust  then  be  1.31 — 1^0.31. 

Applying  this  to  the  weights  of  the  gases  ol>tained 
above  we  would  have: 

2.090  kg.  CO2 
0.453  kg.  H2O 
0.060  kg.   SO; 
5.900  kg.  N: 
7.66.0.31=2.370  kg.  Air 

It  might  be  added  that  the  gas  samples  were  taken  as 
close  to  the  kiln  as  possible,  so  as  to  avoid  the  dilution 
caused  by  the  leakage  of  air  into  the  flue  near  the  damper. 

In  calculating  the  heat  lost  by  the  waste  gases  during 
any  given  period  we  must  first  obtain  the  ratio  of  the  heat 


A    STUDY    OF    HEAT    DISTRIBUTION     IN     FOUR    INDUSTRIAL     KILNS. 


carried  out  by  the  gases  evolved  from  1  kg.  of  eoal  at  the 
flue  temperature  to  the  heating  value  of  this  weight  of  coal. 

In  this  calculation  there  are  necessary  the  weight  of 
waste  gases,  their  thermal  capacity  and  the  flue  tempera- 
ture. 

The  specific  heats  of  the  gases,  as  taken  from  the 
standard  tables  are  not  suitable  for  the.se  calculations, 
since  they  apply  only  to  a  temperature  range  between  0° 
and  100 ^C,  and  if  used  would  cause  a  more'  or  less  grave 
error.  The  work  of  Le  Chatelier  and  Mallard*  has  clearly 
shown  tliat  the  thermal  capacity  of  gases  is  exj^ressed  by 
a  parabolic  formula  of  two  parameters: 

T  T^ 

in  which  Qu=heat  capacity. 

a=a  constant  comon  to  all  gases=fi.5. 

T=absolute  temperature. 

b=a  constant,  variable  for  diiferent  gases. 

The  value  of  b  for  perfect  gases  like  On,  N21  H2  ^^^^^^ 
CO  is  O.G,  for  luO  2.9,  and  for  CO2  3.7.  This  formula 
applies  only  to  the  molecular  volume  of  each  gas  at  abso- 
lute temperatures.  For  the  sake  of  convenience  it  is  pre- 
ferable to  calculate  the  values  in  terms  of  one  kg.  and  the 
temperature  in  degrees  C.  This  has  been  done  in  the 
following  table  :t 


THERMAL  CAPACITY 

OF  I    KG.  GAS,   IX   KG. 

CALS. 

Temperature  in 

Oxygen 

N'itrogen.  Carbon 

1 

Steam 

Carbon  Dioxide 

degrees  C. 

Monoxide 

0 

0.0 

0.0 

I 

0.0 

0.0 

200 

47-3 

50.0 

100. 0 

43-1 

400 

88.0 

100. 0 

203 . 0 

91.0 

600 

1.34-0 

154-0 

1      326.0 

145.0 

800 

181. 0 

207.0 

!        461.0 

208.0 

1000 

232.0 

264.0 

!        609 . 0 

277.0 

1200 

284.0 

3^5-0 

770.0 

354  0 

1400 

334  0 

383-0 

943-0 

435-0 

*Tndustrial  Furnaces  and  Methods  of  Control.     Emilio  Damour,  p.  li. 
Metallurgical   Calculations.     J.   W.  Richards. 

tindustrial  Furnaces  and  Methods  of  Control.     Emilio  Damour,  p.  13. 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  7 

By  plotting  a  curve  from  these  data  for  each  gas  the 
heat  capacity  of  1  kg.  of  the  gas  can  be  read  off  at  once 
for  any  temperature.  This  was  done  in  the  work  under 
discussion.  For  the  purpose  of  illustration  let  us  take 
the  figures  obtained  above  for  the  weights  of  the  gases,  and 
assuming  that  the  gases  left  the  kiln  ot  620 "C  we  would 
have  the  following  heat  capacities,  the  atmosplieric  tem- 
perature being  20°. 

2.09  X145    =303.05  kg.  cals.,  heat  capacity  of  CO2 
0.453X326    =147.68  kg.  cals.,  heat  capacity  of  H2O 
0.453X80+0.453X537    =279.50  kg.  cals.,  heat  of  vaporization  of  HoO 
5.9     X154    =908  00  kg.  cals.,  heat  capacity  of  Ni 
2.37  X  149.4=354.08  kg.  cals.,  heat  capacity  of  air 

l992.3l^total   heat   carried   out  by  waste  gases. 

If  the  calorific  power  of  the  coal  used  is  0200,  it  is 
evident  that  the  heat  lost  by  the  waste  gases  must  be 

1992 

equal  to  ^^^^jX  100^52.13  per  cent.    For  every  100  pounds 

of  coal  fired  we  thus  lose  in  the  waste  gases  32.13  pounds. 

The  temperature,  as  has  already  been  stated,  was  ob- 
tained by  means  of  the  Le  Chatelier  thermocouple,  inserted 
into  the  flue  close  to  the  kiln.  Corrections  were  made  for 
the  atmospheric  temperature.  This  was  done  by  fastening 
a  thermometer  to  the  junction  between  the  platinum  and 
the  copper  wire.  The  correction  is  equal  to  0.5  of  the  ther- 
mometer reading  where  the  atmospheric  temperature  does 
not  exceed  40°.  In  very  hot  places  the  correct  procedure  is 
to  insert  the  copper  junction  in  boiling  water  and  to  cali- 
brate the  couple  under  these  conditions.  The  calibration 
is  to  be  made  by  means  of  the  melting  points  of  zinc,  silver 
and  gold  or  copper. 

In  the  losses  due  to  the  waste  gases  must  be  included 
also  the  loss  due  to  the  escape  of  combustible  gases.  Under 
the  conditions  of  the  kilns  examined  in  this  work  the 
amount  of  carbon  monoxide  found  in  the  gases  was  very 
small.  Immediately  after  firing  some  of  this  gas  was 
found,  but  it  disappeared  in  a  few  minutes.     For  this  rea- 


8  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 

son  it  was  not  included  in  the  losses  incurred  by  the  flue 
gases.  It  seems  that  the  hot  mass  of  clay  tends  to  promote 
the  oxidation  of  the  combustible  gases  formed  in  the 
furnace. 

D.  The  heat  required  to  raise  the  ware  to  the  ulti- 
mate temperature  of  the  kiln  w^as  calculated  from  the 
weight  of  the  ware,  its  specific  heat  and  the  kiln  tempera- 
ture. The  amount  of  water  contained  in  the  clay  was 
taken  into  consideration.  Unfortunately,  several  import- 
ant constants  are  lacking,  such  as  the  heat  of  dehydration 
of  clay  and  the  heat  of  vaporization  of  the  hygroscopic 
water.  Even  the  specific  heat  of  clay  is  not  known  for  the 
liigher  temperatures,  though  it  is  usually  given  in  text 
books  as  being  0.2.  Mr.  J.  K.  Moore,  during  some  recent 
work  in  connection  with  his  thesis,  found  the  average  ther- 
mal capacity  of  a  burnt  No.  2  fire  clay  between  the  limits 
of  400-1100° C  to  be  0.235.  At  the  time  the  calculations 
for  this  work  were  made  the  specific  heat  of  clay  was  taken 
as  0.2.  The  heat  of  dehydration  was  assumed  to  be  200  gr. 
calories  per  gram  of  water.  No  reliable  data  was  obtain- 
able on  this  subject.  The  latent  heat  of  the  hygroscopic.' 
water  which  leaves  in  the  neighborhood  of  200 '  was  taken 
to  be  476  according  to  the  formula  of  Griffith's, 

L=596.73— O.eOt. 

Assuming  then  a  clay,  containing  2%  of  hygroscopic 
and  7%  of  chemical  water  which  is  to  be  raised  to  1120°, 
we  would  have  for  1  kg.  of  the  dried  clav  the  following 
heat  consumption,  the  atmospheric  temperature  being  20°. 
Tlie  dehydration  temperature  to  be  taken  as  650°. 

Hygroscopic  water  0.02X180X1=    3.6  kg.  calories 

0.02X476    =    9.5  kg.  calories 

Chemical  water   0.07X  .02X650^    9. 1  kg.  calories 

0.07X200        =14.0  kg.  calories 
Clay    , 0.93X0.2X1100=204.6  kg.  calories 

I  kg.  clay  thus  requires   .' 240.8  kg.  calories 

E.  As  has  been  mentioned  above,  the  heat  absorhed 
by  the  kiln  and  lost  by  radiation  was  obtained  by  differ- 
ence. 


A     STUDY    OF    HEAT    DISTRIBUTION    IX    FOUR    INDUSTRIAL    KILXS.  U 

APPARATUS. 

The  apparatus  nsed  in  tliis  work  consisted  of  tlie  Orsat 
gas  apparatus,  two  tin  gas  samplers,  snpported  by  tripods 
and  painted  with  asphaltum  paint,  one  Siemens-Halske 
niilli-voltnieter  and  donble  throw  switch,  two  thermo- 
couples, one  for  the  fine,  the  other  for  the  kiln,  two  ther- 
mometers reading  to  100  C  and  two  to  300°,  the  latter 
being  nsed  during  the  watersmoking  period,  and  two  Rich- 
ardson-Lovejov  metal  draft  gauges,  tilled  with  colored  pe- 
troleum and  showing  a  reading  magnified  four  times. 

The  gas  was  drawn  from  the  flue  through  •>4"  pipes 
l)lugged  at  the  end  and  perforated  around  the  side.  The 
pipe  connected  to  the  draft  gauge  was  provided  with  an 
elbow  so  that  the  end  of  the  pipe  was  parallel  to  the  axis 
of  the  flue  and  pointed  in  the  direction  of  the  stack.  This 
was  found  to  be  important,  giving  more  consistent  readings 
than  when  the  pipe  was  inserted  at  right  angles  to  the  flue. 

KRAFT  GAUGE. 

The  readings  of  the  draft  gauge  were  not  necessary 
for  the  determination  of  the  heat  escaping  through  the 
stack,  since  the  weight  of  coal  actually  tired  was  used  as 
the  basis  of  the  calculations,  but  they  were  useful  in  indi- 
cating the  increasing  velocity  of  the  gases  in  the  stack. 
The  draft  gauge  without  a  Pitot  tube  cannot  be  used  to 
measure  the  velocity  of  the  gases  except  it  is  calibrated 
against  an  anemometer.  A  Pitot  tube  suitable  for  the 
purpose  was  not  available,  since  the  usual  metal  instru- 
ment would  soon  be  destroyed  by  the  high  temperature  of 
the  gases  and  the  time  was  too  short  for  making  a  clay 
tube  of  this  kind. 

AVith  the  Pitot  tnV)e  the  velocity  of  the  gases  in  tlu^ 
flue  or  stack  is  calculated  from  the  relation. 


where  v=the  velocity  in  feet  or  meters  per  second. 


10  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 

g=i:the  gravity  constant,  32.14  ft.  or  9.8  meters. 

h=real  heiglit  of  the  petroleum  column  in  feet  or  me- 
ters, shown  by  the  draft  gauge. 

clr^iirdensit}^  of  petroleum,  in  terms  of  water  at  4°C. 

d==;density  of  the  gases  at  the  temperature  and  pres- 
sure of  the  stack  or  flue  in  terms  of  water  at  4°. 

The  relation  between  the  real  velocity  as  determined 
by  the  anemometer  and  that  calculated  from  the  Pitot  tube 
is  approximately  1.1 — 1.2,  for  the  velocities  in  question  in 
ceramic  stacks.  The  Pitot  tube  velocities  are  hence  to  be 
multiplied  by  this  factor  in  order  to  obtain  the  real 
velocity.* 

Some  erroneous  conceptions  are  current  in  regard  to 
the  meaning  of  the  draft  gauge  readings.  The  value  indi- 
cated by  the  gauge  does  not  represent  the  total  magnitude 
or  "head''  of  the  draft,  but  only  that  part  of  it  which  cor- 
responds to  the  velocity,  of  the  gases  and  which  is  not  avail- 
able for  pulling  the  gases  through  the  furnaces  and  kiln. 

The  total  head  of  draft  which  may  be  expressed  in 
inches  or  millimeters  of  water  or  air  at  0°  is  the  pull  ob- 
tained by  a  stack,  measured  by  the  difference  in  the  weight 
of  the  hot  gases  occupying  the  chimney  and  the  weight  of 
the  same  volume  of  air  at  atmospheric  temperature.  To 
illustrate,  assuming  a  stack  10  meters  high  and  1  square 
meter  in  cross  section  at  273° C,  with  the  atmospheric  air 
at  0°,  we  have  a  difference  in  weight  as  follows:  The 
weight  of  10  cubic  meters  of  air  (volume  of  stack)  at  0°C= 
12.93  kg.  The  weight  of  the  same  volume  of  air  at  273°= 
6.465  kg.  We  have,  then,  as  the  measure  of  the  total  draft 
the  weight  of  12.93-6.465=6.465  kg.  This  weight  is  dis- 
tributed over  the  cross  section  of  1  sq.  meter=^10000  sq.  cm. 
The  pressure  upon  1  sq.  cm.  is  thus  0.65  gram.  This  cor- 
responds to  a  height  of  a  water  column  of  0.65  cm.  Ex- 
pressed in  terms  of  air  at  0°  it  is  0.65X772=501.8  cm., 
water  being  772  times  as  heavy  as  air  at  the  same  tempera- 


*W.  D.  Harkins  and  R.  E.   Swain.     Jour.  Am.  Chem.   Soc,  Vol.  29, 
p.  970. 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  11 

ture.  This  head  of  5.02  meters  represents  the  total  draft. 
But  only  part  of  it  is  available  for  forcing  the  air  needed 
for  combustion  into  the  furnaces  and  pulling  out  of  the 
kiln  the  gases  produced.  Part  of  this  force  is  taken  up  by 
the  velocity  of  the  stack  gases  and  part  of  it  by  the  friction 
of  the  gases  in  the  stack.  The  head  available  tor  the  kiln, 
then,  is  equal  to  the  total  head  minus  the  velocity  and 
friction  heads. 

The  velocity  head  is  calculated  from  the  relation 

V2 

K=-  . 
2g 
Assuming  the  A^elocity  of  the  gases  in  the  above  stack 
to  be  G  meters  per  second,  the  velocity  head,  l^,  becomes 
36 

h,= =1.84  m.,  in  terms  of  air  at  273°. 

2X9.8 
Reduced  to  terms  of  air  at  0"  tliis  head  becomes  0.02ni. 
According  to  Richards  the  friction  head,  Ih,,  of  a  stack  is: 

H 
h.,=1.9-K 
d 
where  H=lieight  of  stack. 

d=diameter  or  side  of  chimney. 
k=constant,  whose  average  value=0.08. 
Substituting,  we  obtain 
10 
ho=l .  0— .  0 .  08=0 .  15  meters. 
1 
The  head  of  the  stack  thus  available  for  pulli3Jg  the 
gases  through  the  kiln=5.02  -  (1.84+0.15  »=3.03  meters 
of  air  at  0°. 

Experimentally,  the  total  head  of  a  stack  may  ])Q  de 
termined  by  suddenly  dropping  the  damper  and  ol)serving 
the  draft  gauge  reading  instantly.  The  common  idea  tliat 
the  draft  of  a  kiln  is  increased  greatly  as  the  stack  be 
comes  very  hot  is  not  true.     It  is  true  that  the  draft  in- 


12  A    STUDY    OF    HrlAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 

creases  up  to  a  certain  temperature  but  not  beyond  it,  in 
spite  of  the  fact  tbat  the  velocity  of  the  gases  increases. 
But  as  Ave  have  seen,  increased  stack  velocity  means  in- 
creased loss  in  available  head.  It  must  be  remembered 
that  the  draft  of  a  stack  is  not  measured  by  the  volume  of 
the  gases  drawn  off,  but  by  the  weight  of  gas  removed  per 
unit  time. 

We  have  thus  the  expression : 


n„         Sd  y    2ff  0.00366. L  (ti-t2)       , 

UU^^^^ ^^ where 

^  If  0.UO366  ti 

Qu=the  weight  of  the  gases  removed  per  second. 
S   =cross  section  of  stack, 
d   =density  of  the  gases  at  0°. 
g    =9.8  m.  OT  32.14  feet. 
L  =lieiglit  of  stack. 

ti  =mean  temperature  of  the  gases  in  the  stack  in 
degrees  C 

t    ^temperature  of  the  air  in  degrees  C 


Since  here  Sdi    2  g  0.00366  L=constant  we  may  say 

that  Qu^K "i"^  u. 00366  tT 

By  differentiation  or  grajjhical  determination  of  the 
maximum  value  of  Qu  we  find  that  the  temperature  at 
which  the  greatest  weight  of  gases  is  removed  is  at  273°C. 
Nothing  is  gained,  therefore,  as  far  as  the  available  draft 
of  a  stack  is  concerned,  by  maintaining  a  mean  stack  tem- 
perature higher  than  273^  above  the  atmospheric  tempera- 
ture. 

SEWER  PIPE  KILN. 

The  kiln  in  (juestion  was  one  of  the  older  kilns  on  the 
plant  and  was  rectangulai-,  its  dimensions  being :  Length, 
42  feet,  width,  17i(-.  feet,  height,  19  feet,  inside  measure- 
ments. It  was  set  with  double  strength  20  inch  pipe, 
nested  with  smaller  sizes,  and  contained  120,460  pounds  of 
clay,  all  told,  including  rings,  etc. 


A    S1*UDy    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  13 

In  burning,  87,335  pounds  of  coal  were  used,  which 
had  the  following  composition: 

Carbon    59-76% 

Hydrogen    •. 4.08% 

Oxygen  and  Nitrogen  10. 72% 

Sulphur    2.57% 

Ash    11.74% 

Moisture   11.13% 

The  ash  was  found  to  show  tlie  following  analysis : 

Carbon    29.17% 

Hydrogen   0.26% 

Oxygen  and  Nitrogen  3 .  13% 

Sulphur    3 .  16% 

Ash    68.99% 

Moisture    1 .  55% 

The  calorific  power  of  tlie  coal  was  6,020  calories,  or 
10,837  B.  T.  U. 

The  weights  of  tlie  gases  from  1  kg.  of  coal  were: 

CO;=2.070  kg. 

H-0=o.478  kg. 

N==5.76S  kg. 

assuming  perfect  combustion.  The  weight  of  air  re((uired 
per  kg.  of  coal  is  7.48  kg. ;  3.42  per  cent  of  carbon  were  lost 
in  the  ashes. 

The  length  of  the  burn  was  129  hours.  This  was  di- 
vided into  10  periods  of  12  hours  and  one  of  9  hours.  All 
the  analyses  and  other  data  were  averaged  on  the  basis  of 
the  12  hour  period,  care  having  been  taken  to  make  the 
analyses  representative  of  the  average  conditions. 

In  Fig.  1  we  have  represented  the  average  coal  con- 
sumption per  hour  during  the  burn.  Fig.  2  shows  the 
time-temperature  curves  of  the  kiln  and  flue.  In  Fig.  3 
there  are  shown  the  average  carbon  dioxide  and  air  per- 
centages for  each  period  throughout  the  burn. 

HEAT  LOST  BY   WASTE  GASES. 

In  calculating  the  heat  passing  off  with  the  waste 
gases  from  the  data  represented  by  the  above  curves,  the 
mean  flue  temperature  from  the  beginning  to  the  end  of 
each  period  was  taken  and  the  atmospheric  temperature 


14  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


TRANS.  AM   CER  5nc.    VOL  X 


FIGl. 
SEWER  PIPE  KILN. 

FUEL  CONSUMPTION  PER  HOUR. 


BLtlMINCiER. 


14-00 

\ 

\ 

\ 

1000 

\ 

\ 

/ 

800 

\ 

\^ 

/ 

N 

I 

oc 

^    600 
oc 

UJ 

Q- 

< 

o 
o 

o  400 

in 

o 
Z 

/ 

/ 

o 

200 

/ 

^ 

k 

n  i' 

A 

r 

24 


HOURS 


7i 


96 


120 


(lediictecl.  The  heat  carried  out  by  the  gases  correspondiiiij; 
to  1  kg.  of  coal  was  then  calculated,  as  shown  in  th(^  first 
part  of  this  paper.  In  the  case  of  the  sewer-pipe  kiln  the 
waste  heat  of  each  period  is  given  in  the  folloAving  table : 


A     SlUDV    or    HKAT    IMSTRlIiUTlON     IN     FOUR    INDUSTRIAL    KILNS. 


16 


00 


ON 

00 


^ 

1-4 
00 

HH 

H4 

fO 

J^ 

CO 

fO 

O 

IN 

01 

l^ 

CO 

VO 

r:: 

N 

00 

N 

HH 

n 

bo 


Ah 


^ 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


16 


T«ANS    AM    CER-  50C.    VOLX 


BLEININGER 


FIG  Z. 
SEWER  PIPE  KILN. 

TIME-TEMPERATURE    CURVE. 


1100 

/ 

^ 

900 

J^ 

— ' 

y 

i  /tio 

/ 

1 

5 

1 

J 

J 

\^P^ 

, j^ 

] 

y 

k  j 

> 
y 

/- 

^^ 

^>< 

Y 

„' 

.^i:::!!--. 

^-J — ' 

h-r 

2  3 

PAYS 


TRANi    AM.  CER    SOC       VUL  X 


FIG5. 
SEWER  PIPE  KILN. 

AVERAGE  CARBON  DIOXIDE 

Sc 

AIR    CONTENT    OF  FIRE  GA6E5. 


A    ?TUDV    OK     KI:AT    DISTUIIiL'TION     IX     FOL'R    INDUSTRIAL    KILNS.  I( 

Adding  up  the  pounds  of  coal  wliioh  express  the  loss 
of  heat  by  the  ^vaste  gases  we  obtain  16351  pounds.  Since 
tlie  total  coal  fired  was  87,330  pounds,  it  is  evident  that 
the  heat  escaping  through  the  flue  is  equal  to  18.6  per  cent. 
Fig.  4  shows  the  losses  for  each  period  of  the  burn. 

HEAT   IlIXiUIUEI)   TO   BURN   THE   WARE. 

Calculating  the  heat  required  to  burn  120,160  pounds 
of  clay,  as  illustrated  above,  to  a  temperature  of  1100° 
there  will  be  used  13,689,179  kg.  calories,  which  equal 
4987  pounds  of  the  coal  employed  in  this  case.  This  cor- 
responds to  5.71%  of  the  total  heat  introduced  into  the 
kiln. 

HEAT  LOST  IN   THE   ASHES. 

The  carbon  lost  in  the  ashes  amounts  to  3.42%  of  the 
coal.     Since  practically  no  available  hydrogen  was  found 


TRAN5     AM   CER     50C      vOl  X. 


B  L  1 1  M  I  N  Ci  t  rs 


F1G4-. 
SFWER   PIPE  KILN. 
%HEAT    LOST    BY  WASTE 
GASES    IN  TERMS   OF  HEAT   INTRODUCED. 


18 


A    STUDY    OF    HKAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


in  the  ashes,  the  heat  lost  in  this  way  evidently  is  0.0342 X 
8080  kg.  calories  per  kg.  of  coal.  Calculating  this  loss  in 
percentage  we  obtain  4.58%. 

HEAT  TAKEN  UP  BY  THE  KILN  AND  LOST  BY  RADIATION. 

The  heat  coming  under  this  heading  is  evidently  ob- 
tained by  subtracting  the  sum  of  18.6%+o.Tl%-f-i-58% 
from  100  which  gives  us  71.1%,  a  very  high  percentage, 
approaching  the  similar  losses  of  open-hearth  steel  fur- 
naces and  must  be  ascribed  to  the  poor  condition  of  the 
kiln. 

In  Fig.  5  the  draft-gauge  readings  are  plotted,  ex- 
pressed in  draft  gauge  divisions  and  inches.  The  gauge 
was*frequently  set  to  the  zero  point  to  allow  for  the  evapor- 
ation of  the  petroleum. 


TRANS.  AM.  CER    SOC.     VOL  X. 


FIG  5. 
5EWER  riPE  KILN. 
DRAFT  GAQE  CURVE. 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  19 

Collecting;  the  data  obtained  in  these  calculations  we 
find  the  heat  distribution  to  be  as  follows : 

Heat  lost  by  the  fire  gases    18.6  % 

Heat  taken  up  by  the  ware  5.7  % 

Heat  lost  by  ashes  4.58% 

Heat  taken  by  kiln  and  lost  by  radiation 71 .  i  % 

100.0% 
In  burning  looo  kg.  of  ware  there  were  used  4378341  kg.  cals. 
In  burning  i  ton  of  ware  there  were  used  3984200  kg.  cals. 
In  burning  i  ton  of  ware  there  were  used  1456.8  lbs.  of  coal 
Temperature  iioo°C. 

Durinji'  saltinj;  the  fire  gases  were  found  to  contain 
15.6%  COo  and  2,4%  O^.  An  interesting  fact  observed  was 
also  that  the  temperature  during  salting  rose  5°  in  spite 
of  the  fact  that  the  reactions  involved  in  salting  are  endo- 
thermic,  thus  showing  that  there  is  no  diflflculty  in  main- 
taining sufficient  heat. 

During  the  latter  part  of  the  burn  some  carbon  mon- 
oxide was  found  in  the  gases,  but  only  for  a  short  time  and 
in  small  amounts.  The  loss  of  heat  due  to  this  source  was 
hence  neglected, 

r.wixf;  r.KicK  kiln. 

This  kiln  was  a  2(1  ft.  round  down  draft  kiln  and  con- 
tained 357,204  pounds  of  burnt  clay.  The  amount  of  coal 
used  was  121,028  pounds.  The  maximum  temperature 
reached  was  1110°O. 

Analysis  of  coal : 

Carbon     60.15% 

Hydrogen    4.15% 

Sulphur    4-34% 

Oxygen   and   Nitrogen    9-37% 

Ash    14.09% 

Moisture    7 .90% 

The  calorific  power  was  found  to  be  6231  or  11216  B. 
T.  U, 

Analysis  of  ashes: 

Carbon    21 .  53% 

Hydrogen     0.11% 

Sulphur 1.81% 

Oxygen  and  Nitrogen   0.83% 

Ash" 77.30% 

Moisture    ,,,.,.,,.,.  o .  08% 


20 


A    STUDY    OF    HKAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


Thus  3.03%  of  carbon  in  the  coal  was  lost  with  the 
ashes. 

From  1  kg-,  of  this  coal  there  would  be  evolved  : 

2.090  kg.  carbon  dioxide 
0.453  kg.  steam 
5.900  kg.  nitrogen 


TRANS.  AM.  CER.  SOC.    VOLX 


BLElNINGER. 


800 


700 


600 


500 


4-00 


300 


200 


100 


FIG  6. 

PAVING  BRICK  KILN. 
FUEL  CONSUMPTION  PER  HOUR. 


3  A 

PA-rs. 


•  5 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  21 


TRANS   AM.   CER    SOC     VOlX. 


FIG  7. 
FAUINO  BRICK  tllLN. 

TIME  -TEMrER/VTURE                                                         , 

ii.                          y^^''-^     V ' 

DRAFT  GAOE  CURVE5  -                            /     ^^IZSn  : 

>V                      'y"^           ^\ 

y^^^^'^^^^A' 

cr                            / 

i 

^c 

« 

/  i                 L---^ 

'       i        1    .-T--J 

!     }'  i 

l\ 

i  \ 

/ 
/ 

/ 

/           -^ 

^             /         ^1 

\ 

/ 

r-^_ 

V 

/       1 

/         / 

1         A 

Vh 

/      /: 

/ 

T 

/ 

/> 

I 

i 

f 

y 

j 

r' 

/ 

i 

/ 

1 

/ 

1 

1 

1 
4 

> 

! 

— 

.-' 

— 

> — f 

not  eoiisiderino-  the  siilpliur  dioxide  and  assuming  perfett 
conditions  of  combustion.  For  eadi  kg.  of  uoal  tired  tliere 
would  have  to  be  introduced  7.(10  leg.  of  air  for  theoretical 
combustion. 

The  length  of  the  burn  was  204  hours. 

The  coal  consumption  per  hour  is  shown  in  Fig,  0  for 
each  period  of  12  hours  throughout  the  burn.  Fig.  7  gives 
the  time-temperature  curves  for  the  kiln  (couple  intro- 
duced on  top)  and  the  flue  as  well  as  the  draft  gauge  read- 
ings. The  latter  are  taken  from  the  stack,  and  it  must  be 
remembered  that  each  division  equals  3,4  inch  and  that  the 
readings  are  magnified  four  times.  Each  division  thus 
corresponds  to  3-16  inch  of  petroleum,  verti-.-al  height.  In 
Fig.  8  the  COo  and  air  contents  of  the  gases  are  repre- 
sented. From  the  air  curve  we  observe  that  the  shale  is 
not  a  difficult  one  to  oxidize,  that  the  air  content  of  the 
gases  is  not  excessive,  and  the  heat  losses  are  not  so  much 
due  to  large  air  excess  as  to  the  high  exit  temperature  of 
the  waste  gases. 


22 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


TRANS    AM.   CER    &0C     VOl  X 


FIGS. 

PAVING  -  BRICK    KILN. 

AVERAGE  CARBON  DIOXIDE 
AIR  CONTENT  OF  FIRE  GASES 


BLEININaER 


< 

K 

\ 
\ 

^ 

io 

70 

\ 

\ 
\ 

\ 

\ 

i 

^ 

i 

V    ; 

^ 

k 

/ 

^ 

Y 

A 

i 

\ 

) 

i 

\ 

A 

)\ 

(     ] 

i 

\ 

/ 
/ 

\ 

\ 

i 

k 

y 

\ 

l\ 

+0 
> 

y 

1 

r-N 

i-'r- 

/\ 

{ 

s 

T 

n  A-YS 


HEAT  CARRIED  OUT  BY  WASTE  GASES. 


Proceeding  as  before  we  can  calculate  the  heat  carried 
out  into  the  flue  from  the  weight  of  coal  fired  per  period, 
the  air  content  of  the  gases  and  the  flue  temperature,  so 
that  we  have  the  followino-  results : 


A    STUDY    OF    HF.AT    UISTKI  IK'TlOX     IN-POIR    INDUSTRIAL    KILNS. 


23 


'      o-           o 

o 

o 

i        1 

00 

CO 

VC 

^ 

T                  ^,                    Oil 

00 

00 

H- 1 

oi             ^      1         1 

^J^_ 

^c 

N 

00 

OO                 i^                "^ 

8 

^  1  ^ 

d           Z           ^ 

►H 

^ 

'^    ^ 

0\                  lO                  ir; 
r^                i-c                    -On 

VO 

^       i       "                 1 

l^                w                 O 

— 

1— ( 

^        1         ^                % 

^ 

=^     --^ 

1/- 

>        8    1    ° 

?J.       1 

^           ,^          o     . 

■^ 

^   :   ^  1    r,    \ 

.r 

Tf            ]£'           cc 

-^ 

2 

o      1 

vo             (;;,             in 

HH 

00 

IN                    I^ 

V^            «      i       N      ; 

-1 

r           o\             •            o 

r^ 

^   ,  ^  i   ^  ! 

1^              00                « 

R     "^     ^ 

f 

{^           ^j 

o; 

On       i           Z             \C        ; 

M 

OO 

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►H 

^        ^        -'    i 

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C                    O 

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^^                                  O 

w 

rt              o- 

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J             o- 

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c              ^ 

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It 

•r:            be 

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C 

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r 

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l;                      O 

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bib 

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:           J3 

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1 

d 

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1 

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1- 

rt               ^ 

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3                ^ 

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24 


A    STUDY    OF    HEAT    DISTRIBUTION     IN    FOUR    INDUSTRIAL    KILNS. 


Adding  the  pounds  of  coal,  wbicli  are  equal  to  the  heat 
wasted  by  the  fire  gases,  we  obtain  36,454  pounds,  which  is 
29.9%  of  the  total  amount  of  coal  fired,  or  we  may  say  that 
the  kiln  shows  a  flue  loss  of  29.9%.  Fig.  9  shows  the  heat 
loss  per  period  graphically. 


TRANS.  AM.  CER   SOC.    VOL  X 


FIG  9. 

rAYING-BRlCK   KILN. 

%HEAT  LOST   BY  WASTE  QA5E5  TER  PERIOP 

IN   TEHMS  OF  HEAT  INTRDPUCEf. 


BLEININGER 


HEAT  REQUIRED   IN   HEATING  UP   THE   WARE. 

Calculating  the  amount  of  heat  theoretically  necessary 
to  raise  the  clays  to  1110° C,  as  shown  above,  we  find  that 
this  heat  is  equal  to  13,778  pounds  of  coal,  which  is  11.3% 
of  the  total  amount. 


HEAT  LOST  BY   UNBURNT   CARBON   IN   THE   ASHES. 

Since  the  carbon  lost  by  the  ashes  is  equal  to  3.03%  of 
the  coal,  the  heat  lost  in  this  way  must  be  equal  to 
8080X0.0303=245  calories,  or  3.9%  of  the  calorific  value 
of  the  coal. 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  25 


HEAT  TAKEN   UP  BY  THE  KILN   AND  LOST  BY  RADIATION. 

This  necessarily  must  be  equal  to  100  —  45.1^54.9%. 
Suminai'izino-,  we  have  the  following  heat  distribution  : 

Heat  lost  by  the  waste  gases 29.9% 

Heat  taken  up  by  the  brick 11 .3% 

Heat  lost  by  carbon  in  the  ash 3-9% 

Heat  taken  up  liy  the  kiln  and  lost  by  racTiation 54-9% 


100.0% 


In  this  kiln  and  under  the  conditions  of  the  test  car- 
ried on 

1000  kg.  burnt  clay  required  2056230  kg.  calories. 
I  ton  burnt  clay  required  1871169  kg.  calories. 
I  ton  burnt  clay  required  660  pounds  of  coal. 
Temperature  iiio''C. 

TERRA  COTTA  KILN.      A. 

This  kiln  was  a  muffle  kiln,  the  muffle  being  16  ft.  in 
diameter.  The  kiln  was  set  with  42,423  pounds  of  green 
terra  cotta  and  2t),!)C0  pounds  of  supports,  kiln  blocks,  etc. 
The  coal  consumed  was  29,340  pounds,  and  the  duration 
of  the  burn  was  G7  hours.  The  maximum  temperature 
reached  in  the  muffle  was  1080  ^C. 

Coal  analysis : 

Carbon    66.78% 

Hydrogen 4.81% 

Sulphur    0.84% 

Oxygen  and  Nitrogen  _. 9.68% 

Ash    7  •  59% 

Moisture    10.30% 

Calorific  power  6716  or  12090  B.  T.  U. 

Analysis  of  ashes: 

Carbon    20.92% 

Hydrogen   0.06% 

Sulphur    0.35% 

Oxygen  and  Nitrogen  0.53% 

Ash    77-94% 

Moisture    0.20% 

Assuming  theoretical  combustion,  the  weight  of  the 
gases  developed  from  1  kg.  of  coal  is  2.39  kg.,  carbon  diox- 


26  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


rtlaNj  AM  CEi*    50C    vClX 


BLEIMNQER 


&0U 


500 


*00 


300 


FIG  10. 

TERRACOTTA  KILN  A. 

COAL  CONSUMPTION  PER  MOUR. 


'  3 


TRANS     AM    CEfl    30C  VOLX 


BlCini  N  r, cr^ 


Fia  II. 

TERRACOTTA  KILN  A. 

TIME  -TEMPERATURE, 
CURVES. 


HOURS 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


ide,  0.553  kg.  steam,  and  5.8  kg.  nitrogen,  the  sulpliur  being 
neglected.  The  air  introduced  under  the  same  conditions 
would  be  7.54  kg. 

Fig.  10  shows  the  average  coal  consumption  per  hour 
for  each  period  of  12  hours.  It  is  seen  to  differ  from  the 
corresponding  curve  for  the  open  kilns  by  the  compara- 
tively small  tiuctuations  in  the  amounts  of  fuel  fired,  as  is 
to  be  expected  from  this  type  of  kiln.  The  time-tempera- 
ture curve  is  given  in  Fig.  11.    The  COo  and  air  curves  of 


TRANi.    AM     CER    iOC      VOLX. 


BlEinin&er 


Fig.  12  indicate  strongly  oxidizing  conditions  throughout 
the  burn.  The  draft  gauge  readings  have  been  rejected 
owing  to  the  rather  unsatisfactory  place  at  which  the  gauge 
was  connected  to  the  flues  surrounding  the  muffle. 

HEAT  CARRIED  OUT  BY  THE   WASTE   GASES. 

Proceeding  with  the  calculation  of  the  flue  loss  we 
can  tabulate  the  results  as  follows: 


28 


A    ?TUDY    OF    HEAT    DTSTRlBUriON    IN    FOUR    INDUSTRIAL    KILNS. 


I 

2 

3 

4 

5 

6 

Kg.  calories  lost  per  kg.  of  coal 

741 

1102 

1476 

1 954 

2622 

2510 

%  of  liear  lost  in  terms  of  heating 

II. 0 

16.4 

22.0 

29.1 
1830 

39-0 
2214 

37-4 

Pounds  of  coal  lost  by  waste  gases 

per    period    

396 

876 

1248 

1017 

Addinji'  up  the  amounts  of  coal  we  have  7581  pounds, 
whicli  is  25.8%  of  the  total  amount  of  fuel  used,  21),:U0 
pounds.  In  Fig.  13  the  average  heat  losses  per  perio<l  are 
shown  graphically. 

HEAT  REQUIRED  TO  BURN  THE  WARE. 

Calculating  the  heat  theoretically  required  to  Imrn 
the  terra  cotta  and  to  heat  up  the  supports,  we  find  that 
this  amounts  to  3,G88  pounds,  or  12.57%  of  the  total  heat 
introduced. 

HEAT  LOST  BY  CARBON  IN  THE  ASHES. 

The  carbon  lost  with  the  ashes  amounts  to  1.6%  of  the 
coal.  Thus  the  heat  lost  in  this  way  is  (8080X0.016)-^ 
671(5 X  100^1.9%.  In  this  kiln  the  grates  were  in  excellent 
shape,  and  this  explains  the  low  loss. 

HEAT  TAKEN  UP  BY  THE  KILN  AND  LOST  BY  RADIATION. 

It  is  evident,  then,  that  the  loss  must  be  equal  to 
100-  (25.8+12.57+1.9)=59.73%. 

Summarizing,  the  heat  distribution  i  ;  ..s  r;.:;ows: 

Heat  lost  by  waste  gases  25 .  80% 

Theoretical  heat  necessary  to  heat  up  charge 12.57% 

Lost  by  carbon  in  the  ashes i  .90% 

Heat  taken  up  by  kiln  and  lost  by  radiation 59-73% 

100.00% 


A    STUDY    OF    HEAT    DISTRIBUTION     IN     FOUR    INDUSTRIAL    KILNS.  31) 

1000  kg.  terra  cotta  under  these  conditions  required 
5113775  kg.  eals.=1675  pounds  of  coal. 

1000  kg.  terra  cotta  plus  supports:  o007i.M)5  kg.  cals. 
=985  pounds  of  coal. 

1  ton  terra  cotta  required  1521  pounds  of  coal. 

1  ton  terra  cotta  plus  supports  896  pounds  of  coal. 
Temperature=1080°C. 

In  taking  several  samples  of  gas  from  the  muffle  during 
the  raising  of  tlie  heat,  3%  of  CO^  Avere  found. 

TERRA   COTTA   KILN.      B. 

This  kiln  was  constructed  entireh^  differently  from 
the  preceding  one.  Its  inside  muffle  diameter  was  2V6'%  its 
height  17  feet  high  in  the  center  and  12  feet  to  the  spring 
of  the  arch.  The  charge  consisted  of  113,280  pounds  of 
terra  cotta  and  75,691  ])ounds  of  kiln  stonefs  and  supports. 
The  fuel  used  amounted  to  81.420  pounds  of  coal.  Length 
of  binii,  115  hours.  The  kiln  was  well  built  and  in  excel- 
lent coiulition.     The  maxiiiniiii  tcmjx'rature  was  1115°C. 

Analysis  of  coal : 

Carbon    69 .  30% 

Hydrogen    4.62% 

Sulphur    1 .  64% 

Oxvgcn  and  Nitrogen   9-94% 

\sli    6.55% 

.Moisture 7-95% 

Calorific  power  6961,  or   12330  B.  T.  U. 

Analysis  of  ash : 

Carbon    20 .  53% 

Hydrogen    o .  22% 

Sulphur    0.51% 

Oxygen  and  Nitrogen i  .03% 

Ash    77.40% 

Moisture    0.31% 

1.34%  of  carbon  was  lost  in  the  ashes.  1  kg.  of  coal 
resulted  in  2.49  kg.  carbon  dioxide,  0.495  kg.  of  steam,  and 
6.97  kg.  nitrogen,  assuming  theoretical  combustion,  and  1 
kg.  of  coal  required  under  these  conditions.  8.24  kg.  of  air 
for  combustion. 


30 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


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A    STUDY    OF    HEAT    DISTKIBUTION    ]N    FOUR    INDUSTRIAL    KILNS.  31 

TRANS  AM.  CtR   50C      VOL  X-  BLtlNINOER 


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the  tiuie-temperature  curves  for  the  kiln  and  the  flue  as 
well  as  the  draft  gauge  readings.  It  is  sIioaau  here  that 
the  fire  gases  leave  at  a  very  high  temperature  and  that 
hence  a  large  flue  loss  is  to  be  expected.     The  difference 


32  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


TRANS   AM    CER    SOC.     VOLX. 

FIG16.  TERRA  COTTA  KILN  B. 

TIME  -   TEMPERATURE 


BLEININOER 


TRANS    AM    CEH    SOC       VOLX. 


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A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 


33 


in  construction  between  kilns  A  and  B  is  brought  out 
clearly  by  these  curves.  Fig.  16  illustrates  the  average 
carbon  dioxide  and  air  contents  of  the  fire  gases  represent- 
ing for  each  period.  It  is  observed  that  in  this  kiln  also 
the  conditions  are  decidedly  oxidizing. 

HEAT  LOSSES  DUE  TO  THE  FLUE  GASES. 

The  results  of  the  calculations  ai-e  again  indicated  in  a 

table,  viz : 

in 


34 


A     ?TUDY    OF    HEAT    DISTRIBUTIOX     TN    FOUR    INDUSTRIAL    KILNS. 


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A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL     KILNS.  35 

Fig.  17  slioAvs  the  percentage  of  heat  lost  during  each 
period. 

Adding  up  these  amounts  of  coal  we  find  that  the 
pounds  of  coal  lost  bj  the  waste  gases  are  e(iual  to  40,478 
pounds,  or  57.1%  of  the  total  amount  of  coal,  81,420 
pounds. 

HEAT  REQUIRED  TO  BURN  THE  WARE. 

By  calculation  the  theoretical  amount  of  heat  rerjuired 
to  burn  the  terra  cotta  and  heat  up  the  supports  was  equal 
to  6514  pounds,  or  8%  of  the  total  amount  of  coal. 

HEAT  LOST  BY  UNBURNT  CARBON  IN  THE  ASHES. 

Since  the  carbon  lost  to  the  ashes  amounts  to  1.34%, 
the  percentage  heat  loss  due  to  this  cause  is  [(8080X 
0.0134)-^696i]Xl00=1.6%. 

HEAT  TAKEN   VV   I5Y  THE  KILN   ANI>  LOST  BY   RADIATION. 

This  is  equal  to  100— (57.1+8.0+1.6)=33.3%.  This 
item,  therefore,  is  very  small  for  this  kiln,  which  speaks 
well  for  its  construction. 

Summarizing,  we  have : 

Heat  lost  by  the  waste  gases 57  •  i  % 

Theoretical  heat  required  for  charge   8.0% 

Heal  lost  by  unburnt  carbon   i  .6% 

Heat  lost  to  kiln  and  radiation   33-3% 

1000  kg.  terra  cotta  required  5002518  kg.  calories. 
1000  kg.  terra  cotta  and  supports  307242^  kg.  calories. 
I  ton  terra  cotta  required  1439  pounds  of  coal. 
I  ton  terra  cotta  and  supports  884  pounds  of  coal. 
Temperature  iii5°C. 

It  will  be  observed  that  in  spite  of  the  large  flue  loss 
in  kiln  B  and  the  higher  muffle  temperature  the  efficiency 
is  about  the  same  as  that  of  A,  this  being  due  to  the  larger 
size  and  hence  greater  tonnage  of  B. 

For  the  sake  of  completeness  the  writer  desires  to 
quote  the  results  obtained  for  a  brick  kiln,*  burning  hard 

♦The  Clay  Worker,  February,  1908. 


36  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 

shale  building  and  sewer  brick.  This  kiln  was  of  the  down 
draft  type,  28  feet  inside  diameter,  and  contained  66,190 
brick,  each  weighino-  6%  pounds.  The  amount  of  coal  con- 
sumed was  1)5,045  pounds,  the  B.  T.  U.  value  being  11162. 
The  summary  of  the  heat  distribution  of  this  kiln  was  as 
follows : 

Heat  lost  by  the  flue  gases  27.33% 

Theoretical  heat  required  to  burn  bricks 19-55% 

Heat  lost  by  unburnt  carbon   3-51% 

Heat  taken  up  by  kiln  and  lost  by  radiation 49.61% 

100.00% 

1000  kg.  of  brick  recpiired  1,119,171  kg.  calories,  or  for 
eadi  ton  of  ware  168  pounds  of  coal  were  fired.  The  tem- 
perature was  1100°  C. 

Comment  on  the  work  of  this  article  is  hardly  neces- 
sary since  the  figures  themselves  are  the  conclusions  to  be 
drawn.  It  might  facilitate  comparison  to  arrange  the  ab- 
solute quantities  of  heat  required  in  each  case. 

1000  kg.  sewer-pipe    4378341  kg.  calories 

1000  kg.  paving  brick    2056230  kg.  calories 

IQOO  kg.  terra  cotta,  A    4640756  kg.  calories 

1000  kg.  terra  cotta  plus   supports    3007205  kg.  calories 

1000  kg.  terra -cotta,  B   5002518  kg.  calories 

1000  kg.  terra  cotta  plus  supports   307242;^  kg.  calories 

1000  kg.  hard  building  brick    I449I74  kg.  calories 

Expressing  these  values  in  pounds  of  coal  per  ton  w(i 
have : 

I  ton  sewer  pipe    1457  pounds  coal 

I  ton  paving   brick    660  pounds  coal 

T  ton  terra  cotta,  .A.*    1524  pounds  coal 

I  ton  terra  cotta  and  supports    896  pounds  coal 

I  ton  terra  cotta,   B I439  pounds  coal 

I  ton  terra  cotta  and  supports    884  pounds  coal 

I  ton  building  brick    468  pounds  coal 

In  conclusion  the  writer  wishes  to  acknowledge  his 
indebtedness  to  Professor  C.  W.  Rolfe  for  having  granted 
the  use  of  the  funds  and  apparatus  which  made  the  work 
possible.  He  also  desires  to  express  his  appreciation  of  tlie 
conscientious  services  and  faithful  cooperation  of  Mr.  C. 

*The  coal  used  in  \  is  inferior  in  heating  value  to  that  in  B. 


A    STUDY    OF    HEAT    DISTRIBUTION     IN     FOUR    INDUSTRIAL    KILNS.  0( 

E.  Merry,  of  the  departmeut  of  ceramics,  Uui\ersit3'  of 
Illinois.  He  wishes  to  thank  especially  the  firms  whose 
kind  ooperatiou  was  enjoyed  in  every  case. 

DISCUSSION. 

Mr.  Laufjcnbrch- :  I  wish  to  ask  about  the  percent  loss 
of  waste  gases — I  presume  by  that  the  speaker  means  both 
the  lost  heat  of  the  gases  during  the  combustion  of  the 
kiln  and  tlie  lieat  loss  by  radiation,  not  only  from  the  out- 
side during  the  burning,  but  also  during  the  cooling  of  the 
ware  through  the  stack.  Did  you  attempt  in  any  waj^  tak- 
ing the  temperature  on  the  outside  of  the  kiln  at  the  var- 
ious points  and  times  to  determine  what  the  percent  of  this 
loss  was,  this  radiation  of  the  kiln  shell  during  the  com- 
bustion? 

Mr.  Bliiniiif/rr:  I  have  made  no  attemjtt  to  do  this 
since  this  is  a  very  difficult  matter,  no  reliable  data  being 
at  hand  to  serve  as  the  starting  point  of  such  calculations. 
The  German  Government  is  endeavoring  to  obtain  the 
necessary  facts  by  experimental  researches.  There  is  ab- 
solutely no  reliance  to  be  ])laced  on  any  data  found  in 
handbooks  concerning  radiation.  There  are  any  number 
of  theoretical  calculations  on  this  subject,  but  tiiey  do  nor 
agree  in  their  deductions. 

Mr.  Laiifjcnhrck :  1  am  gla<l  the  German  (lovernment 
is  investigating  thi.s  for  it  is  a  matter  of  vital  imj)ortan(  e. 
Firing  a  kiln  is  i)iling  up  heat  in  its  shell,  and  we  usually 
thnk  only  that  the  infiow  must  be  greater  than  the  outflow. 
At  the  same  time  a  large  and  increasing  amount  of  heat 
is  being  radiated  on  the  outside;  and  while,  relatively,  fire 
brick  work  is  a  poorly  conducting  substance,  yet  it  is  by 
no  means  as  poor  as  it  ought  to  be;  and  this  is  one  of  the 
gross  defects  of  our  kilns.  We  simply  go  on  building  ivilns 
of  fire  brick  instead  of  more  effective  insulating  material, 
instead  of  using  hollow  brick.  The  saving,  entirely,  aside 
from  the  possible  saving  in  fuel,  is  in  the  steadier  accumu- 
lation of  heat  in  the  kiln  by  a  lessened  radiation  from  the 


3S  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 

outside.  The  011I3'  larger  practical  work  I  have  attempted 
aloug  this  line  was  iu  building  a  kiln  at  the  Mosiac  Tile 
Co.,  in  Zanesville,  Ohio,  where  I  left  an  air  space  between 
the  fire  brick  lining  and  red  brick  outside,  and  1  held  the 
fire  brick  lining  in  place  by  a  header  brick  which  extended 
an  inch  or  an  inch  and  a  half  beyond  the  red  brick.  But  I 
was  not  able  to  follow  it  up  properly  and  cannot  give  you 
any  data,  because  the  question  is  too  difficult,  as  IMr.  Blein- 
inger  says,  and  it  was  a  very  insignificant  trial  to  make. 
But  I  believe  if  pottery  companies  will  make  up  their  minds 
to  pay  a  little  more  for  hollow  fire  brick  and  put  up  their 
kilns  of  them,  it  will  be  worth  while. 

Another  question  I  wish  to  ask.  In  pointing  out  the 
loss  of  fuel  in  firing,  in  the  beginning,  Mr.  Bleininger  says 
that  it  is  necessarily  much  greater  than  in  a  boiler.  Is 
that  your  idea? 

Mi\  Blcimngcr:  Yes,  sir,  not  in  the  b(\iiinning  so 
much  as  later  on. 

Mr.  Lajigcnhccl-.  I  can  understand  that  the  greatei' 
the  temperatures  the  greater  the  loss  by  radiation  and 
gases  might  be,  but  your  statement  might  be  subject  to  the 
misinterpretation,  as  that  a  high  temperature  apparatus 
like  a  kiln  is  more  wasteful  in  its  work  than  a  low  temper- 
ature apparatus  like  a  boiler.  When  we  introduced  gas  at 
the  Mosaic  Tile  Co.,  it  proved  more  economical  to  fire  our 
kilns  with  gas  than  with  coal  but  not  our  boilers,  and  we 
returned  to  coal  for  firing  the  boilers.  The  kiln  as  an 
apparatus  is  much  more  economical  of  fuel,  in  my  exper- 
ience, measured  by  dollars  and  cents,  than  boilers,  because 
the  latter  in  its  work  chills  the  fire  gases  below  the  com- 
bustion temperature,  the  former  does  not. 

Mr.  Blewiiiger:  I  was  referring  to  the  effect  pro- 
duced. In  the  boiler  you  are  getting  effect  measured  by 
water  evaporation ;  in  the  kiln,  by  the  burning  of  the  ware 
to  a  certain  temperature.  From  this  standpoint  it  is  more 
economical  than  the  kiln. 

Mr.  Langeuhecl-.  I  wanted  to  bring  out  what  might 
be  misinterpreted  in  that  point. 


A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS.  39 

Mr.  Wlieelcr:  We  certainly  are  deeply  indebted  to 
Mr.  I^leininger  for  this  ver^^  valuable  contribution,  show- 
ing what  we  do  not  knoAv.  lie  has  put  a  magniticent 
amount  of  work  there,  and  the  facts  are  very  clearly  and 
concisely  stated. 

I  will  ask  one  ([ucstion  to  bring  out  one  point  more 
clearly.  Were  those  kilns  selected  under  normal  condi- 
tions, with  the  common,  everyday  firing,  «>r  were  they 
s]){^cially  tired  by  expert  workmen,  and  vras  there  any 
handling  of  the  kilns?  I  will  also  ask  Mr.  Bleininger,  in 
that  loss  which  he  ascribes  to  radiation  and  kiln  loss, 
whether  he  attempted  to  r(Highly  differentiate  between  the 
external  shell  loss  and  what  might  be  safely  deducted  as 
not  external  radiation?  If  he  could  give  us  a  hint  on  that 
it  wouhl  be  greatly  appreciated. 

J//".  Blciniiu/cr:  I  have  not  attempted  to  do  this. 
r>ut  in  one  case  where  the  conditions  were  favorable,  where 
tlie  air  was  being  drawn  out  of  the  kiln  by  a  fan,  we  at- 
tempted to  measure  the  heat  retained  in  the  kiln.  We  in- 
serted a  pyrometer  and  later  on  thermometers  into  the 
goose-neck,  and  knowing  the  ])ressure  exerted  by  the  fan 
we  were  able  to  roughly  <alculate  the  velocity.  I  have  not 
finished  the  work,  but  we  shall  be  able  to  calculate  the 
weight  of  the  air  and  the  temperature,  and  therefore 
roughly  the  heat  taken  by  the  fan  from  the  kiln.  In  other 
plants  the  conditions  have  not  been  favorable. 

Answering  the  first  ([uestion,  I  will  say  that  tlie  con- 
ditions were  the  ordinary  ciuiditions,  no  expert  help  being- 
employed.  I  asked  the  superintendents  to  take  no  special 
precautions,  but  to  let  things  go  on  in  their  usual  way. 
^Ir.  Merry  can  tell  us  how  he  found  conditions. 

Mr.  Merry :  As  to  whether  the  kilns  were  the  average 
or  not,  I  think  the  sewer  pipe  kiln  was  the  worst  on  the 
yard.     The  others  were  about  the  average  kiln. 

Mr.  Atihrey :  I  will  ask  Mr.  Bleininger  what  he  cal- 
culates the  heat  retained  by  the  ware?  Is  that  heat  taken 
to  perform  the  mechanical  action  in  the  clay  ware? 

Mr.   Bleiningei^:     The  calculated  heat  includes   that 


4'>  A    STUDY    OF    HEAT    DISTRIBUTION    IN    FOUR    INDUSTRIAL    KILNS. 

required  for  the  expulsion  of  the  mechanical  water,  the 
raising  of  the  heat  of  the  clay  itself  from  the  atmospheric 
temperature  to  the  final  temperature,  and  that  taken  by 
the  expulsion  of  the  chemical  water.  We  have  no  accurate 
figures  in  regard  to  the  heat  of  decomposition  of  the  hy- 
drous clay  substances.  I  have  assunied  it  to  be  200  calories 
per  gram  of  such  water. 


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